1. Field of the Invention
The present invention relates to a proximity-type sensor.
2. Description of the Related Art
There is a great need for sensors, or detectors, that contain no movable parts, that are soft and pliable, and that can be produced in shapes and sizes that suit the field of use for which they are intended. Several different types of proximity sensors for indicating the presence of people or objects are known to the art. Examples of such sensors include different types of membrane contacts, infrared detectors, etc. These known sensors, however, are more or less complicated and in certain cases expensive. There is also a need for an inexpensive and simple contactless sensor that is able to detect, or sense, the presence of a person or an object without coming into contact therewith. It is also desired to be able to produce very thin sensors of this kind.
The present invention relates to a sensor that can sense the presence of a person or an object either without or by coming into contact with said person or said object, that can be made very thin, that lacks movable parts, and that can be designed to suit the area of use for which it is intended. Accordingly, the present invention provides a sensor for indicating changes in the physical presence of persons or objects, and is characterized in that the sensor includes at least two electrically conductive sheets of material that are spaced mutually apart on an electrically non-conductive carrier sheet or the like; and in that a sensing circuit is provided for sensing changes in the capacitance between electrically conductive sheets.